In the future on the serpentine belt, 2 ways to do it :

1. using a pull handle and 17 mm socket, relieve the tension and place a suitable sized hex wrench in the hole of the tensioner, then release the pressure.
( the hole is at about 4 oclock when viewed from the front )
It will stay in place and you can easily take off and replace the belt. Reverse to remove the pin when new belt in place.

2. Without using a pin, just relieve the pressure and remove the belt.
When putting back on, place it around all the pulleys except the idler above the alternator, then use the wrench to tension the tensioner pulley and pop the belt over that last idler.
This is the way I have always done it.

If you are doing something in the front engine area, it helps to remove the radiator fan.
Easy to do, remove the two top clips, unplug the plug then wiggle it up and out past all the radiator hoses.